Astronomers have discovered what is probably the most distant galaxy yet seen in the Universe by combining the power of the NASA/ESA Hubble Space Telescope, NASA’s Spitzer Space Telescope and one of nature’s zoom lenses. The object offers a peek back into a time when the Universe was only 3% of its present age of 13.7 billion years.
We see the newly discovered galaxy, named MACS0647-JD, as it was 420 million years after the Big Bang. Its light has travelled for 13.3 billion years to reach Earth, which corresponds to a redshift of approximately 11.
This is the latest discovery from the Cluster Lensing And Supernova survey with Hubble (CLASH), which uses massive galaxy clusters as cosmic telescopes to magnify distant galaxies behind them, an effect called gravitational lensing
“While one occasionally expects to find an extremely distant galaxy using the tremendous power of gravitational lensing, this latest discovery has outstripped even my expectations of what would be possible with the CLASH program,” Rychard Bouwens (Leiden University, Netherlands), a co-author of the study said.
“The science output in this regard has been incredible,” he said
Along the way, 8 billion years into its journey, the galaxy’s light took a detour along multiple paths around the massive galaxy cluster MACS J0647.7+7015. Due to the gravitational lensing, the team observed three magnified images of MACS0647-JD with Hubble. The cluster’s gravity boosted the light from the faraway galaxy, making the images appear far brighter than they otherwise would, although they still appear as tiny dots in Hubble’s portrait.
“This cluster does what no man-made telescope can do,” Marc Postman (Space Telescope Science Institute, USA), leader of the CLASH team said. “Without the magnification, it would require a Herculean effort to observe this galaxy,” he added.
The object is so small it may be in the first stages of galaxy formation, with analysis showing the galaxy is less than 600 light-years across. For comparison the Milky Way is 150 000 light-years across.
The estimated mass of this baby galaxy is roughly equal to 100 million or a billion suns, or 0.1-1% the mass of our Milky Way’s stars. “This object may be one of many building blocks of a galaxy,” Dan Coe (Space Telescope Science Institute), lead author of the study said.
“Over the next 13 billion years, it may have dozens, hundreds, or even thousands of merging events with other galaxies and galaxy fragments,” he added. The team spent months systematically ruling out all other alternative explanations for the object’s identity before concluding that it is the distance record holder.
This was important, as nearby objects (such as red stars, brown dwarfs and old or dusty galaxies) can mimic the appearance of an extremely distant galaxy and must be carefully excluded.